#1
What exactly is involved in changing and biasing the preamp tube on a VJ? I googled it but had no luck.
#2
Preamp tubes do not need to biased. You should not need to bias the power tube either. As for whats required to bias, I hear its a little more involved than most amps. I do believe it's mentioned in the VJ resource thread, which is where this should be.
#4
O.o for realz? that may kill my wanting to buy one, because I want to learn fully about tubes.
#5
The bias is already set in the vj but they're a tad hot so you'd want quality tubes to put in.

I have JJ 12AT7 (60% of 12AX7) and JJ EL84 in my vj combo.
#6
Quote by CJRocker
Preamp tubes do not need to biased. You should not need to bias the power tube either. As for whats required to bias, I hear its a little more involved than most amps. I do believe it's mentioned in the VJ resource thread, which is where this should be.
True.

The preamp tube is cathode biased, class A. Changing the bias will affect the gain a bit, but the power dissipation of the tube will always be small, compared with it's maximum rating. The fact that it's biased by a resistor in series with the cathode will make it tolerant of a wide variety of tubes, with less change in characteristics, other than gain.

But changing the biasing will shift the output of each stage closer to cut-off or saturation. This is a bit more important in the second stage, especially if you install a master volume and drive that stage to clipping.
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#7
The only biasing info you need for preamp tubes, is if you're fiddling with the circuit. It doesn't really affect their output or whatever, but it affects tonal characteristics... In general though, a hot biased preamp tube will give a Marshall vintage crunch, and a cold one will give you a dry sound Mesa Recto crunch.

You shouldn't really need to adjust the bias of the EL84 as it's in cathode bias and should be set about right from the factory.
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